a) many of them would appoint their own family members (or, if we forbade that, would find someone to swap off with),
Um.. Isn't it impossible because of the one character per continent policy? And swapping is punishable as per "no placeholders" rule. Nothing new here.
b) the old clique in a situation like that above would be able to maintain their power even through a coup, as they could ensure that all the positions their people occupied remained within their group essentially forever
If the old clique had all the position of power a coup would be impossible. If they had most of those positions, it's actually good if they get to keep them and remain a counter-balancing power, otherwise you'd essentially swap one clique for another.
c) in general, it would just be terrible for turnover, especially for positions which are presently elected, as even if you managed to wound, capture, or even kill the "old guard" guy holding the spot, rather than getting to replace him with someone new and fresh, you would be 100% guaranteed that his buddy, also part of the old guard, would be the one to get the position.
Firstly, we're talking about positions requiring appointment. Electable positions are.. well, electable. You can't hog them.
Secondly, once again I can't see how this makes it easier for the old guard to maintain control. Why do you keep insinuating that every lord setting his heir will lead to more corruption than only a single Duke making all the decisions? Can't you see this can not be right logically?
